TSE 2451 / TSR 2701 Software Requirements Engineering

Tutorial 6

1. Explain the fundamental concepts behind of data-flow modelling; illustrate your answer

with an example. What is a common criticism of data-flow diagrams?

2. Consider a simple auto-teller machine (cash point). The machine accepts customer

requests and dispenses cash, displays and prints out mini statements, and provides the

bank manager with a daily transaction report. Users interact with the ATM through a

video display unit and a keypad. An ATM user must have a valid cash-card and Personal

Identification Number (PIN) before he or she can access the services of the ATM. Cash

withdrawals must be less than or equal to the user’s balance. Apart from providing

services to its user, the ATM is also required to update the customer account database

each time there is a cash withdrawal. The bank manager uses a staff PIN to access the

system for transaction reports.

Construct a two-level DFD of the ATM showing the services that are provided.

3. Identify possible objects for the ATM system described in question 2 and classes.

Construct an object model of the ATM system.

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